A power converter achieves high-efficiency power conversion by a high-speed switching operation of power-conversion semiconductor elements. The high-speed switching operation is, however, also a source of electromagnetic noise. Electromagnetic noise can also cause malfunctions in power converters itself or peripheral electronic equipments. Therefore, a reduction in electromagnetic noise is an important technical issue to be addressed for developing power converters.
To address such an issue, PTD 1 (Japanese Patent No. 4548004) describes that in a PWM (pulse width modulation) inverter consists of a single-phase AC power supply, a diode rectifier, a smoothing capacitor, and an inverter, a larger capacitor than an output-side capacity of an inverter is connected between one end of a DC bus portion and the ground, resulting in reduction of noise.